With the development of HDTV and high-end multimedia information system, existing video signal program sources can no longer meet people's needs for visual effect; thus it is necessary to improve the frame rate of existing video program sources to achieve better visual effect. Meanwhile, although high compression ratios have been obtained in current video transmission encoding and decoding technologies, to adapt to some applications with limited bandwidth, the space-time resolution of video signals is usually decreased to reduce data further. Such data reduction can be achieved by frame skip at the encoding end in the time domain. Thus, video with low frame rate at the decoding end inevitably leads to discontinuous motion and degradation of image quality, especially in scenes comprising fast movements and complex details. To address this issue, video frame interpolation, that is, Frame Rate Up-Conversion (FRUC) technology can be used at the decoding end to restore the original frame rate, to improve the visual effect of images. Moreover, this technology can also be used for conversion between video formats with different frame rate. By inserting intermediate frames between adjacent frames, the low frame rate of video is raised to high frame rate to achieve the conversion between different frame rates.
The current mainstream frame rate up-conversion method is based on motion compensation interpolation using block matching. However, the block-matching algorithm includes an essential flaw: at the edge of the object, the regions that do not belong to the same object are assigned into a same block and given a same motion vector, which will cause the blocking effect of the interpolated frame. Moreover, the “conflict” and “hole” problems caused by “shielding” and “exposure” cannot be resolved using the existing methods.
Effectively reducing the blocking effect problem and solving the “shielding” and “exposure” problems have always been the focus of research in this field.